Enzymes

Enzymes

• biological catalysts
• speed up reactions so that the reactions happen at normal body temperature
• globular proteins with tertiary or quaternary structure

Substrate

• reactant
• 2 substrates forming 1 product or 1 substrate forming 2 products
• catabolic or anabolic metabolism

Active Site

• specific shape with active site in enzyme
• region of enzyme where substrate will bond and reaction will occur
• reaction will occur here
• chemical attraction between AS and enzyme
• enzyme and substrate is like lock and key

Denaturation

• enzyme loses conformation and can't function
• separate 2 DNA strands
• extreme conditions of pH, salt concentration, and temperature cause this catalyst change reaction rate without being consumed

Immobilized Enzymes

• in industry
• restrict enzyme movement
• commercial use of 500+ enzymes
• more stable
• uses biotechnology

Biotechnology

• makes products like laundry detergent, textile preparation, biodegradable clothing
• normal production of lactase, which breaks lactose into glucose and galactose
• makes yeast, which makes lactase
• helps in lactose intolerance

3 steps in catalysis

1. Substrate(s) bond to active site (s)
2. Substrate turns to a product bound to the enzyme
3. Active Site releases the product and can catalyze other substances

Substrate Movement

• random movement in water
• substrate smaller and faster than enzyme
• random movement causes collision which causes enzyme-catalyzed reaction

Enzymes & Temperature

• temperature increase causes enzyme efficiency to increase until a certain point
• once that point is crossed, the enzyme denatures

Enzymes & pH

• optimum pH of 7
• activity level reduced with pH change

Enzymes & Substrate Concentration

• directly proportional
• until all enzymes are active
• then no effect on concentration

Cofactors

• nonprotein enzyme helpers
• inorganic or organic
• organic includes coenzymes
• coenzymes include vitamins

Enzyme Inhibitors

• slow down enzyme reaction rate
• competitive or noncompetitive
• ex. toxin, poison, pesticides, antibiotics

Competitive Inhibitor

• binds to enzyme's active site
• directly competes with the substrate

Competitive Inhibitor Graph

• same Vmax
• lower Km

Noncompetitive Inhibitor

• binds to other part of enzyme
• denatures it, making it less useful
• same Km, lower Vmax

Noncompetitive Inhibitor Graph

• same Km
• lower Vmax

Enzyme Regulation

• chemical chaos if cell's metabolic pathways weren't tightly regulated
• cells switch genes encoding certain enzymes on and off or regulating enzyme activity

Allosteric Regulation

• inhibit or stimulate enzyme
• regulatory molecule binds to enzyme at one site and affects action at another

Allosteric Regulation & Inhibition

• most allosteric-regulated enzymes made from polypeptide subunits
• active and inactive forms
• activator binding and inhibitor binding

Activator binding site

• stabilizes the active form of the enzyme

Inhibitor Binding Site

• stabilizes enzyme's inactive form

Feedback Inhibition

• end-product of metabolic pathway shuts down the pathway
• prevents a cell from wasting chemical resources by synthesizing extra product

Assumption of a Steady State

• transient phase where ES concentration does not change during the reaction (dES/dt) = 0 Km
• substrate concentration where V0 = (1/2) (Vmax)

Enzyme classification

• uses a number system

Enzyme Classes

• Oxidoreductase

  • transfer electrons in Redox reactions to catalyze oxidation or reduction
  • oxidation
  • reduction in electrons
  • increase oxidation state
  • reduction
  • increase in electrons
  • decrease oxidation state

• Transferase

  • transfer functional groups between molecules

• Hydrolase

  • break bonds by adding H2O

• Lyase

  • elimination reactions to form double bonds
  • remove hydrogen and carbon

• Isomerase

  • aka utase
  • intramolecular arrangements
  • one of the "weirder" enzymes

• Ligase

  • join molecules with new bonds metabolism
  • total of organism's chemical reactions
  • emergent property from cellular molecule interactions

Metabolic Pathway

• begins with a specific molecule and ends with a product
• chain of reactions
• enzymes catalyze each step

Catabolic pathways

• release energy by breaking down complex molecules into simpler ones
• ex. cellular respiration

Anabolic Pathways

• use energy to build complex molecules from simpler ones
• ex. protein synthesis from amino acids

Bioenergetics

• the study of how organisms manage their energy resources

Energy

• the capacity to cause change
• exists in various forms
• some forms can perform work

Kinetic energy

• energy associated with motion
• Heat (thermal energy)
• kinetic energy
  • associated with the random movement of atoms of molecules

Potential Energy

• energy that matter possesses because of its location or structure

Chemical Energy

• potential energy available for release in a chemical reaction

Thermodynamics

• the study of energy transformations

Isolated System

• isolated from its surroundings
• ex. liquid in a thermos

Open System

• energy and matter can be transferred between the system and its surroundings
• ex. organisms

First Law of Thermodynamics

• energy of the universe is constant
• energy can't be created or destroyed, only changed
• principle of conservation of energy

Second Law of Thermodynamics

• during every energy transfer or transformation, some energy is unusable, and is often lost as heat
• each change increases the entropy (disorder) of the universe

Spontaneous Processes

• occur without energy input
• they can happen quickly or slowly
• increase entropy of the universe

Biological Order and Disorder

• cells create ordered structures from less ordered materials
• organisms replaced ordered forms of matter and energy with less ordered forms
• energy flows into an ecosystem as light and out as heat

Exergonic Reaction

• net release of free energy
• spontaneous

Endergonic Reaction

• absorbs free energy from its surroundings
• nonspontaneous